The present invention relates to a vehicle seats, in particular to hydraulically or fluid powered adjustable automotive vehicle seats.
In order to comfortably accommodate various sizes and shapes of occupants vehicle seats are generally provided with various adjustment mechanisms to adjust the position of the seat within the vehicle and/or move various movable portions of the seat. Typically vehicle seats are provided with fore and aft adjustment, and the seat back is pivotally mounted to a seat bottom cushion such that the angle of the seat back to the bottom cushion of the seat can be adjusted. Other adjustment and adjustment mechanisms may also be provided to for example adjust the height of the vehicle seat, angle and tilt of the seat bottom cushion, position of the headrest, and/or the lumber support. The seat adjustment mechanisms may be manually operable, or increasingly some or all may be power operated. Conventionally such power operated adjustment mechanisms comprise separate electric motors mounted within the seat driving each adjustment mechanism though suitable gearing. The individual motors are controlled via switches operable by the seat occupant with a central seat adjustment control unit often being incorporated.
Whilst such electrically powered adjustable seats are commonplace, the electric motors and associated gearing can often be relatively and undesirably noisy as well as providing often jerky movement and adjustment. As increasing seat adjustment, and powered seat adjustments, are demanded and provided the number of electric motors required also increases. This increases costs and weight of the vehicle seat and furthermore the additional motors and gearing take up increasing space within the seat assembly.
Hydraulic or fluid powered seat adjustment mechanisms have been proposed instead of the electric powered systems. Indeed the earliest of such proposals date back a number of years. A distinction should however be drawn between hydraulic or fluid powered adjustment systems, and the more basic and simple and hydraulic locking systems and/or damper arrangements.
In such hydraulic or fluid powered arrangements pressurised fluid, provided from a pump, is supplied via a control valve to piston/cylinder actuators. These actuators move and directly adjust the position of the seat or portions of the seat to be adjusted. Such hydraulic powered arrangements offer the prospect of extremely quiet, near silent, operation, without the noisy mechanical gearing. Smooth and almost infinitely variable adjustment is also possible with such hydraulic powered arrangements.
In spite of these, and other, advantages of hydraulically powered seat adjustments they have not been adopted for widespread automotive vehicle seat use over the considerable number of years since they have initially been proposed. Overall, and although hydraulics are used in other areas in automotive vehicles (for example braking systems), those skilled in the art of vehicle seat design would not generally from a practical stance consider using hydraulic powered seat adjustment systems. Indeed the conventional trend is away from hydraulics in general in automotive applications and to electric powered systems.
One of the main reasons for this is the cost of such previously proposed hydraulic systems. It is also perceived that such hydraulic systems are complex. In addition to comply with automotive crash loading requirements the seat must provide sufficient structural strength and withstand high crash loading without failing or allowing excessive movement of the seat or portion thereof. In particular under crash loading the forces applied to the seat may generate extremely high pressures, for example in the region of 1700 bar, within the hydraulic system and pump, pipework and actuators. The hydraulic system must be capable of withstanding these high crash loading pressures. This increases the sizing of the pipework, pump and actuators and the quality to which they must be made and assembled and the resultant costs.
It is therefore desirable to provide an improved hydraulically powered automotive vehicle seat adjustment system which addresses the above described problems and/or which offers improvements generally.